Abstract: The upper Wuerhe formation of Upper Permian in District Wuba of Karamay oilfield in the northwestern margin of Junggar basin is a set of terrigenous coarse-grained clastic rocks. The main reservoir of the formation is sandy conglomerate and there are always some disputes on its sedimentary facies: alluvial fan, alluvial fan-fan delta or alluvial fan-nearshore subsea fan-fan delta. Further study on lithofacies will be benefit for accelerating the hydrocarbon exploration and development in the study area. By integrating data of core, rock thin section, lab analysis, mud log and well logging, the paper performs in-depth study on sedimentary characteristics of the formation. The study results show that the sedimentary facies of the upper Wuerhe formation in the study area is not an alluvial fan with its composite deposition system, but a set of typical fan delta depositions including 9 microfacies, i.e., fan channel, debris flow and underwater distributary channel and so on. The paper also defines relationships between lithofacies and sedimentary microfacies. It is considered that the the physical property, oil-bearing property and formation test productivity of tractive-current sandy conglomerate are better than those of gravity-current sandy conglomerate, which could provide geological theory basis for future oil and gas exploration and development in the area